1. It is proposed to study in detail the metabolic steps involving glycine greater than succinyl glycine (NSG) greater than cyclization to 6-keto-tetrahydropyridine -- 2 carboxylic acids in the biosynthesis of homarine by homogenates of shrimp muscle. Chemical synthesis of NSG aldehyde will be attempted to determine if this intermediate undergoes ready cyclization and is biologically converted to homarine. We propose to prepare 13C labeled precursors for biological conversion to homarine which will be analyzed with NMR to investigate the precise location of isotopic carbons. 2. The biosynthesis of quinolinic acid will be investigated by a similar metabolic pathway: malonyl CoA + L-aspartate greater than N-malonylaspartate greater than cyclization greater than quinolinate. 3. Transmethylation studies will be continued with homarine, N-methylquinolinic acid and trigonelline to determine if there is transference of methyl groups between these pyridinium compounds and whether they all serve as methyl donors in crustacea.